1. Field of the Invention
This invention relates to an auxiliary door lock, and in particular to an auxiliary lock for use on the interior operating knob of a dead bolt lock.
2. Discussion of the Prior Art
There are tens of millions of dead bolt locks currently in use in North America. Such locks include a retractable bolt which is operated using a knob on the interior of a door, or using a key in an exterior portion of the lock. All too often, duplicates of keys for operating the locks from the outside of a dwelling fall into the wrong hands. Because of this problem, auxiliary locks for use with dead bolt locks have long been in existence. Examples of such auxiliary locks are found in Canadian Patent No. 2,054,078, which issued to S. P. Meszaros on Dec. 9, 1997; Canadian Patent Application 2,310,971, laid open on Mar. 22, 2001; and U.S. Pat. No. 2,463,195, which issued to P. F. Mungan on Mar. 1, 1949; U.S. Pat. No. 3,748,882, which issued to R. A. Dusault, Jr. et al on Jul. 31, 1973; U.S. Pat. No. 5,901,590, which issued to C. I. Lai on May 11, 1999; U.S. Pat. No. 5,934,122, which issued to T. M. Edwards et al on Aug. 10, 1999; U.S. Pat. No. 6,105,406, which issued to S. G. Thompson et al on Aug. 22, 2000; U.S. Pat. No. 6,145,358, which issued to W.-B. Wu on Nov. 14, 2000 and U.S. Pat. No. 6,301,941, which issued to M. L. Nicholsfigueiredo on Oct. 16, 2001.
Many of the patented devices are somewhat complicated and hence expensive to manufacture and/or difficult to install and operate. Accordingly, there is still room for improvement of auxiliary locks of the type in question.
The object of the present invention is to meet the above defined need by providing a relatively simple auxiliary lock for use with a dead bolt lock which is easy to manufacture, install and operate.
Accordingly, the present invention involves an auxiliary lock for use on the interior operating knob of an exterior key-operated dead bolt lock comprising:
(a) housing means for mounting on the inside of a door over the operating knob of a dead bolt lock;
(b) an opening in said housing means;
(c) actuator means for slidable mounting in said opening and on the knob of a dead bolt lock;
(d) first teeth means in said housing means; and
(e) second teeth means on said actuator means for cooperating with said first teeth means to lock said operating lock in a locked position, whereby, when the actuator means is in a first, unlocked position in the housing means, the dead bolt lock knob cannot be rotated to unlock the door, and when the actuator means is in a second, unlocked position in the housing means, the actuator means and the operating knob can be rotated to unlock the door.